Route calculation method

ABSTRACT

A method for calculating a route from a starting location to a destination location is described; it is characterized in that the route is calculated after specifying at least one pass-through destination location by way of at least one pass-through destination point, which is situated in a circumscribed area of the at least one pass-through destination location specified by a specified criterion.  
     In contrast with the route calculation method known from the related art, the specified pass-through destinations are not part of the trip route, but instead, except for a specified circumscribed area, they function as vaguely specified interpolation points for influencing the route calculation.

BACKGROUND INFORMATION

[0001] The present invention is directed to a method for calculating aroute from a current location to at least one destination location viaat least one pass-through destination location according to the preambleof the independent patent claim.

[0002] Vehicle navigation devices available and distributed today, e.g.,by the company Blaupunkt-Werke GmbH, Hildesheim, allow automatic routecalculation from the current vehicle position to the destinationlocation input (after user input of a destination location), and theyguide the driver of the vehicle along the calculated trip route from theparticular instantaneous vehicle location to the destination location byoutputting trip instructions, preferably acoustic instructions.

[0003] The route calculation is usually performed by taking into accounta specified or user-specifiable optimization criterion such as thequickest or shortest route from the current location to the destinationlocation. There is no provision for taking into account user preferenceswith regard to a certain preferred trip route or a certain preferredsegment of road.

[0004] Such user preferences may be based, for example, on the fact thatthe user has detailed information regarding traffic obstacles on certainroads or segments of roads around which he must detour, or the drivermay prefer known segments of road at the expense of a slight detour incomparison with segments of road with which he is not familiar. Inaddition, user preferences may also be based on a shortening of the timeand/or distance that is possible by giving preference to well-developedstate or federal highways over freeways, for example.

[0005] If the driver of a vehicle would like to be directed from acurrent position to a destination over a certain route, then in the caseof known navigation devices, it is currently advisable to inputintermediate destinations which prompt the navigation device tocalculate a route from the current location to the intermediate locationand from there to the actual destination location and thus to take intoaccount certain preferred sections of road in the route calculation.

[0006] This method has the disadvantage that after the routecalculation, the vehicle is navigated from the current location to thedestination location by way of intermediate destinations input in such away that the vehicle is navigated to the next intermediate destinationuntil actually reaching the intermediate destination. This does notallow passing merely in the vicinity of the intermediate destination, asmight actually be desired.

Advantages of the Invention

[0007] The method according to the present invention having the featuresof the independent claim has the advantage over the related art that itpermits a route calculation via user-defined pass-through destinations(the term “pass-through destination” is used intentionally todifferentiate it from the intermediate destinations mentioned above), sothey are used as interpolation points for forcing certain preferredroads or segments of roads to be included in the route calculationwithout actually having to reach these destinations in a subsequentnavigation. This is achieved according to the present invention by thefact that after at least one pass-through destination location has beenspecified, a pass-through destination point is determined automaticallyfor each of the at least one pass-through destinations, this destinationpoint being situated in a circumscribed area of the at least onepass-through destination location determined by a specified criterion,and the route is calculated via the at least one pass-throughdestination point.

[0008] Thus, the pass-through destination(s) is/are not a part of thetrip route, but instead the pass-through destination(s) is/are passed byonly at a minimum distance defined by the circumscribed area.

[0009] Advantageous refinements of the method according to the presentinvention are characterized in the dependent claims.

[0010] The method according to the present invention is advantageouslyimplemented in such a way that

[0011] in a first step, the starting location is set as the startingpoint for the route calculation, and a first of the at least onepass-through destination locations is set as the pass-throughdestination;

[0012] in a second step, a route segment from the starting point to thepass-through destination point, which is determined automatically and issituated in an interception range around the pass-through destination,determined according to the specified criterion;

[0013] in a third step, the end point (=pass-through destination point)of the previously calculated route segment is set as the starting pointfor the calculation of an additional route segment;

[0014] in the case of additional pass-through destinations, the next ofthe at least one pass-through destination locations is set as thepass-through destination, and the sequence is continued with the secondstep;

[0015] in the case when there are no other pass-through destinationlocations

[0016] in a fourth step, the route segment from the starting point setin the third step to the destination location is calculated, and

[0017] the route is obtained by arranging the calculated route segmentsin a sequence.

[0018] The specified criterion may advantageously be a specifieddistance from the pass-through destination in the form of a fixedlydefined distance value, in the form of a distance value derived fromcalculated route information, in particular the calculated route lengthor a case-specific, fixedly defined distance value or derived fromcalculated route information, depending on which distance value isgreater.

[0019] The specified criterion may also advantageously be a change inthe class of road, which is necessary to reach the pass-throughdestination, in particular a required change from one class of road to alower class of road.

[0020] The specified criterion may also advantageously be one of theaforementioned distance criteria or a change in the class of road on acase-by-case basis, depending on which criterion defines a largercircumscribed area.

DRAWINGS

[0021] Exemplary embodiments of the present invention are illustrated inthe figures and explained in greater detail below.

[0022]FIG. 1 shows schematically a block diagram of the part of anavigation device which is essential to the present invention forimplementing the method according to the present invention;

[0023]FIG. 2 shows a simplified flow chart of the method according tothe present invention.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0024] The present invention is described below using the example of avehicle navigation device which is provided for use in a motor vehicle,and a method of route calculation in a vehicle navigation device.However, this is not to be understood in the sense of a restriction.Instead, the present invention is also equally applicable to navigationdevices intended for other types of applications, e.g., navigationdevices for other means of transport or also as a navigation aid forpedestrians in an area of a city with which they are not familiar. Forthis purpose, it is necessary only to essentially adjust the database ofthe navigation device accordingly. Then in the last case of a navigationaid for pedestrians, specified landmark buildings or comparable landmarkpoints suitable for use as reference points for the route calculation,preferably in the form of roadway intersections, are pass-throughdestinations to be defined by the user. Other intended applications ofthe route calculation method according to the present invention are alsoconceivable and are within the scope of the present invention.

[0025] Navigation device 1 shown in FIG. 1 for implementing the methodaccording to the present invention has position determining means 12 forestablishing a current location of the navigation device or the vehiclein which the navigation device is operated.

[0026] Position determining means 12 include in an essentially knownmanner means for implementing a dead reckoning, i.e., the currentlocation of the vehicle is determined from the distance traveled andinformation regarding the direction of travel.

[0027] For example, the tachometer signal may be used to determine thedistance traveled. This is in turn determined from pulses of radarsensors of an ABS (=anti-lock system) which generate a pulse train as afunction of the rotation of a vehicle wheel, and from a known wheelcircumference. The direction information is determined by a rotationalrate sensor which detects changes in direction, so that the particulardirection of travel at the moment is determinable on the basis of aknown starting direction of travel on the basis of a change in therotational rate of the rotational rate sensor. The current location ofthe vehicle may be calculated in each case from the informationrepresenting the direction of travel and the distance traveled.

[0028] Position determining means 12 also include a receiver for GPS(=global positioning system) signals, i.e., signals emitted viasatellites for determination of position, which also allows the currentvehicle position to be determined.

[0029] Position determining means 12 also include a computing unit whichlinks the position information of the GPS receiver to that of the deadreckoning to form a resultant vehicle position. In addition, theposition determining means compare the vehicle position thus determinedwith traffic route information stored in a bulk memory 14 as aplausibility check and thereby determine a most probable current vehiclelocation. This last step is known as map matching.

[0030] The information determined by position determining means 12regarding the current vehicle location is sent to a controller 10, thefunction of which is explained in greater detail below.

[0031] Bulk memory 14 of navigation device 1 is implemented preferablyin the form of a CD-ROM drive with the data CD inserted, but otherembodiments of bulk memory 14 are also conceivable. Map information, inparticular information regarding the location of landmarks, e.g.,locations and cities together with the particular place namesunambiguously identifying the landmarks, is stored in bulk memory 14. Inaddition, the bulk memory also contains information regarding thetraffic routes connecting these landmarks, such as in particularfreeways and roads of lower road classes such as federal and stateroads, county roads, local through roads, etc. together with a featurecharacterizing the class of road.

[0032] In addition, the navigation device includes a communicationinterface which has an input device, preferably in the form of akeyboard, and an output device, which is preferably visual and acoustic.

[0033] The input device of user interface 16 is used for inputting adestination to which a trip route is to be calculated and then thedriver of the vehicle is to be led. In addition, the input device alsoserves to input one or more pass-through destination locations overwhich the route to be calculated should lead to the destinationlocation.

[0034] The output device supports the user in inputting the destinationlocation or one or more pass-through destinations so that, for example,the letters of a place name that have already been input are displayedvisually on the output device. In addition, proposals selected for placenames on the basis of the letters already input may be offered forselection by the user. The output device is also used for outputting,preferably acoustically, navigation instructions for directing thedriver of the vehicle along the calculated trip route. These destinationinstructions preferably include instructions for turning from the roadon which the vehicle is currently traveling to another road andinstructions regarding the distance to the turning point, e.g., in themanner of “turn left after 100 meters,” etc.

[0035] In addition, navigation device 1 has a destination memory 18 inwhich a destination that has been input via user interface 16 is storedalong with pass-through destination locations that have been input viauser interface 16.

[0036] The components described here, namely position determining means12, bulk memory 14, user interface 16, and destination memory 18 accessa data bus 11 of navigation device 1 which is connected to a controller10 of navigation device 1 and is preferably controlled by thecontroller. In addition, individual components are able to communicateautomatically with other components; for example, the computer ofposition determining means 12 may automatically access bulk memory 14 tocall up map data required for map matching out of bulk memory 14.

[0037] To prevent access conflicts in accessing data bus 11, the accessis handled according to a suitable protocol, e.g., the essentially knownCSMA/CD (=carrier sense multiple access/Collision detection) protocol.

[0038] Controller 10 controls the functions of navigation device 1 andis preferably implemented in the form of an operating program built intoa microprocessor. In conjunction with the present invention, controller10 also has the following functions in addition to the functions knownfor traditional navigation devices:

[0039] receiving the destination and pass-through destination locationsthat have been input via user interface 16;

[0040] allocating the coordinates available in bulk memory 14 for thedestinations and pass-through destinations or allocating otherinformation characterizing the location of the destinations andpass-through destination locations to the destinations and pass-throughdestinations that have been input;

[0041] storing the destination and pass-through destination locationsand the information characterizing their positions in destination memory18;

[0042] sorting the destination and pass-through destination locationsstored in destination memory 18 according to increasing distance fromthe current position of the vehicle or according to decreasing distancefrom the destination location on the basis of a comparison of thecoordinates of the pass-through destination locations with those of thecurrent position or destination; and

[0043] calculating a trip route, optimized according to a specifiedcriterion, from the current position of the vehicle to the destinationvia the pass-through destination locations that have been input usinguser interface 16;

[0044] as explained in greater detail below in conjunction with thedescription of the method according to the present invention.

[0045] In an alternative embodiment of navigation device 1 describedhere for implementing the method according to the present invention, anair interface 15 is connected to data bus 11.

[0046] According to a first variant of the alternative embodiment, airinterface 15 is implemented in the form of a radio receiver which isdesigned for reception and decoding of TMC (=traffic message channel)information transmitted via RDS (=radio data system) by radio in encodedform. According to the first variant of the alternative embodiment, atraffic message memory 141 is provided for storage of the trafficinformation received by radio and is also connected to bus 11 ofnavigation device 1. The traffic messages thus stored are intended tosupplement the traffic route information stored in bulk memory 14. Thenavigation device thus always has current information regarding thecondition of the traffic routes, which is taken into account inperforming an optimized route calculation. This procedure is essentiallyknown as dynamic navigation and therefore needs no further explanationhere.

[0047] According to a second variant of the alternative embodiment, airinterface 15 is designed in the form of a cell phone. Currentinformation regarding the condition of traffic routes may be called upfrom a provider having access to the corresponding data in a mannersimilar to that used in the case of radio. In addition, however, thecell phone also permits partial or complete off-board navigation, as itis called. In this method, after a destination and at least onepass-through destination has been input via user interface 12, this dataand information regarding the current position of the vehicle is sent toa provider. The provider then calculates a route from the currentposition to the destination by way of the at least one pass-throughdestination on the basis of the traffic route information available tothe provider and, if necessary, current information regarding thecondition of these traffic routes. The calculated route is thentransmitted from the provider to the navigation device by way of cellphone 15 entirely or in sections in response to an inquiry and thenavigation device performs a navigation on the basis of the externallycalculated route.

[0048] The method according to the present invention is described ingreater detail below on the basis of the flowchart according to FIG. 2.

[0049] The method begins with starting up the navigation device in step105.

[0050] Then a destination to which a trip route is to be calculated,starting from the instantaneous location of the vehicle, is input in astep 110 by the user using the input means of user interface 16 asexplained below, for example, on the basis of the following examples.

[0051] The driver of the vehicle would like to drive from his currentlocation, e.g., Stuttgart-Feuerbach, to Saarlouis, for example, in theSaarland. The name of the destination is Saarlouis. To input thisdestination place name, the user enters the letter “S.” Then controller10 in the database of bulk memory 14 determines the first place namesbeginning with the letter “S” input. Let us assume this is the placename “Saarbrücken,” for example. In addition, controller 10 triggersuser interface 16 to display the place name “Saarbrücken” thusdetermined, which can then be selected by actuation of a confirmationkey on user interface 16. However, since Saarbrücken is not the desireddestination in the present case, the user will enter the second letter“a” of the destination name. Then the navigation device will suggest thenext place name in the bulk memory beginning with the letters alreadyinput, i.e., “Saarburg,” for example. This procedure is continued untilthe navigation device proposes the desired place name on the basis ofthe letters input or the user has entered the name completely. Theposition information, i.e., preferably coordinates, assigned to theinput destination place name in bulk memory 14 is read out of the bulkmemory by controller 10, which enters this information together with thedestination place names in destination memory 18.

[0052] After concluding input of the destination location, the currentlocation of the vehicle is queried by position determining means 12 viabus 11 (step 115).

[0053] Based on the current vehicle location, navigation device 1 or,more precisely, controller 10 determines a route to the destinationlocation (step 120) with access to the traffic route information storedin bulk memory 14, according to the alternative embodiment using a radioreceiver for reception of traffic information, with additionalconsideration of current traffic route condition information.

[0054] After completing the route from the current vehicle location tothe destination location input, controller 10 controls user interface 16to display the calculated route preferably in the form of a road mapwith landmarks entered such as the names of cities, towns, municipaldistricts, parts of towns or streets and also with labeling of therelevant traffic routes and, for example, the road segments to betraveled may be stored in color, depending on the suitable degree ofdetailing (step 125). In addition, information regarding the length ofthe calculated trip route and a presumed trip duration may also bedisplayed.

[0055] In the case of the example described above of a planned trip fromStuttgart-Feuerbach to Saarlouis, the navigation device calculates aroute as shown by the following description of a route, for example.

[0056] Description of the trip route without user specification ofpass-through destinations: Total Time km km Δ Description Turn RoadDirection 00:00 0 0.1 start on Bregenzer Strasse NW A81 00:00 0.1 0 — on— SW A81 00:00 0.1 0 — bear to left — SW A81 to 00:00 0.1 0.3 — bear toleft B295/ E A81 to Steiermärker strasse 00:01 0.4 0 — half left toB295/Wiener E A81 Platz 00:01 0.4 0.8 — on B295/ NE A81 Borsigstrasse00:03 1.2 0 — continue on Heilbronner E A81 Strasse 00:03 1.2 0.3 — bearto left B10/B27/ NW A81 to Heilbronner Strasse 00:04 1.5 6.6 — bear toB10/B27 NE A81 right on 00:08 8.1 37.7 AK Stuttgart- continue on A81/E41N A81 Zuffenhausen (17) 00:27 45.8 5.9 — continue on A6/E50 NW AKHeilbronn/ Neckarsulm 00:30 51.7 47.2 AK Heilbronn/ continue on A6/E50NW A6 Neckarsulm (37) 00:54 98.9 7.1 AK Walldorf continue on A6/E50 NWA6 (40)(31) 00:58 106 11.1 AD Hockenheim continue A61/E31 N A61 (30)(65)right on 01:04 117.1 14.4 AK Speyer continue on A61/E31 W A61 (63) 01:12131.5 3.4 AK Mutterstadt continue on A61/E31 NW A61 (61)(7) 01:14 134.98.7 AK Ludwigshafen continue on A61/E31 N A61 (60)(5) 01:18 143.6 0.2 AKFrankenthal right, stop — N A6 (21)(59) at 01:19 143.8 0.4 — straight AKFrankenthal N A6 ahead 01:19 144.2 0.5 — right, stop AK Frankenthal N A6at 01:20 144.7 61.4 — straight AK Frankenthal W A6 ahead on 01:50 206.123.6 AK Landstuhl continue on A6/E50 W A6 (12)(10) 02:02 229.7 21.5 AKNeunkirchen continue on A6/E50 SW A6 (8)(27) 02:13 251.2 28 ADSaarbrücken continue on A620 W A620 (3)(22) 02:27 279.2 0.2 ASSaarlouis-Mitte right, stop — NW — (3) at 02:27 279.4 0.8 ASSaarlouis-Mitte bear to B405/Metzer NE — (3) right to Strasse 02:29280.2 0.6 — bear to B405/ SE — right to Ludwigstrasse 02:30 280.8 0.2 —bear to left Lisdorfer Strasse N — to 02:31 281 0.2 — on Französische NW— Strasse [French Road] 02:32 281.2 — destination —

[0057] The procedure described so far is known to be used with thenavigation devices currently available, e.g., from the companyBlaupunkt-Werke GmbH, and therefore requires no further explanation.

[0058] After output of the calculated route, the user has thepossibility of accepting the proposed route or of rejecting it, to whichend a corresponding input is requested by controller 10 via userinterface 16 (step 130). Controller 10 then checks (step 135) on whetherthe proposed trip route has been accepted or rejected.

[0059] If the proposed route has been accepted by a corresponding userinput at user interface 16, the sequence is terminated (step 140). Thenavigation device will then guide the user/driver of the vehicle in aknown manner through output of trip instructions via the output deviceof user interface 16 according to the calculated trip route from thecurrent location to the destination. This navigation procedure isalready associated with current navigation devices available from thecompany Blaupunkt-Werke GmbH of Hildsheim and therefore does not requirefurther explanation.

[0060] In the case of the example described above of the routecalculated for a planned trip from Stuttgart-Feuerbach to Saarlouisaccording to the route description given above, the driver of thevehicle is thus guided from the current vehicle location, namelyStuttgart-Feuerbach, to the next freeway, namely A81, in the directionof Heilbronn, then after the Heilbronn freeway junction, continuing onthe A6 freeway further in the direction of Mannheim, then on the A61freeway after the Heidelberg freeway cloverleaf, traveling in thedirection of Worms; then back on the A6 highway after the Frankenthalfreeway junction, traveling in the direction of Kaiserslautern, andfinally continuing in the direction of Saarlouis after the Saarbrütickenhighway cloverleaf. The total distance thus amounts to 281.2 km and theestimated driving time is 2 hours, 32 minutes.

[0061] However, if the proposed route is rejected through acorresponding user input via the user interface (step 130) and thiscircumstance is ascertained by controller 10 (step 135), then the useris subsequently given an opportunity to indicate one or morepass-through destinations through which the route is to be calculated asa way of influencing the route calculation.

[0062] In the present case, the driver of the vehicle is aware of aroute through the cities of Karlsruhe, Landau and Pirmasens which isactually shorter with regard to the distance to be traveled.

[0063] One or more pass-through destinations (step 145), i.e., in thepresent case the city names of Karlsruhe, Landau and Pirmasens, areinput by analogy with the input of destinations described above via userinterface 16.

[0064] In deviation from the procedure described here, it is alsopossible for the pass-through destination(s) to be input as early asbefore a first route calculation.

[0065] After input of each pass-through destination, it is stored in thedestination memory stored as a pass-through destination data record inthe destination memory together with the information available in bulkmemory 14, the data on the pass-through destinations being flagged todifferentiate it from the data on the destination by using acorresponding identifier assigned to the pass-through destination datarecord.

[0066] After conclusion of the input of the pass-through destinationlocations, the pass-through destination locations and/or thepass-through destination location data records are sorted, preferablyaccording to decreasing distance of the pass-through destinations fromthe destination, in destination memory 18 or, according to a variant, anidentifier characterizing their sequence in destination memory 18 isassigned to the data records on the pass-through destinations.

[0067] Then the following route calculation is initialized. To do so, astarting point for a first section of the route to be calculated isequated (step 150) with the starting location, i.e., the currentlocation which was determined previously (step 115). In the case of theexample given above of the planned trip from Stuttgart-Feuerbach toSaarlouis, this location is Stuttgart-Feuerbach. In addition, thepass-through destination to which the first route segment is to becalculated is equated with the first pass-through destination stored indestination memory 18 (step 155). In the example given above, thepass-through destination is thus determined as the city of Karlsruhe.

[0068] Calculation of a route section after the initialization,performed immediately previously, of the first route section from thestarting point, i.e., the starting location or the current location, tothe pass-through destination (step 160) is performed as follows.

[0069] The route segment is calculated in a manner which is alreadyknown from the previously known navigation devices, for example, withthe main difference being that a route segment is not calculated to thepass-through destination itself, i.e., the city center of the givenpass-through destination city, for example, but instead to a certainenvironment of the pass-through destination, which is calculatedaccording to a specified criterion. The route calculation of the currentroute segment thus ends on reaching the specified environment of thepredefined pass-through destination, so the end point of the calculatedroute segment is in the circumscribed area of the pass-throughdestination.

[0070] The end point of the route segment calculated is determined indetail as follows.

[0071] First, the route calculation algorithm, which is usuallyimplemented in the form of a reverse iterative Ford-Moore algorithm,calculates the route segment from the current position to a preciselydefined point within the pass-through destination. For example, if thecity name “Karlsruhe” has been input as a pass-through destination, thena representative point in the pass-through destination, e.g., the citycenter, or more precisely a certain point in the heart of the city ofKarlsruhe, is determined as the pass-through destination from the bulkmemory. Then a provisional partial route from the current location,i.e., Stuttgart-Feuerbach, for example, to the aforementioned pointwithin the pass-through destination of Karlsruhe is calculated. To doso, the route searching algorithm aligns road segments in succession,starting from the known pass-through destination (Karlsruhe, citycenter) progressively in the direction of the starting location orcurrent location in such a way that the trip duration over the resultantpartial route is minimized. In a next step, the point of intersection ofthe calculated provisional partial route with the circumscribed area ofthe pass-through destination (Karlsruhe, city center) is determined andis set as the pass-through destination point and thus as the end pointof the first partial route so that the resultant partial route ends ator in the aforementioned circumscribed area of the pass-throughdestination.

[0072] Instead of inputting only the place name, for example, of apass-through destination, as an alternative it may also be provided thatthe pass-through destination must be input in input of the finaldestination by a similar procedure, i.e., as input of a precise pointwithin the pass-through destination location, e.g., in the form of boththe place name and the street name. In comparison with the proceduredescribed above, this has the advantage that the software required tocontrol the input of destinations need not be adapted in a complexmanner. A provisional partial route is then calculated to the exactpoint on the pass-through destination thus input, e.g., to a certainstreet within the city of Karlsruhe, the name of which has been input inaddition to the pass-through destination city name of “Karlsruhe.”Otherwise, the pass-through destination point and thus the end point ofthe partial route are determined as described above. Thus thecircumscribed area criterion explained in greater detail above isapplied to the partial route calculated on a provisional basis; forexample, the point of intersection of an imaginary circle having a givenradius about the exact pass-through destination which has been input,with the provisional partial route is determined, and the pointdetermined according to this criterion, i.e., here the point ofintersection of the circle with the partial route determinedprovisionally, is determined as the end point of the partial route.

[0073] The specified criterion defining the environment of thepass-through destination or the interception range around thepass-through destination may include one of the three criteria describedbelow or a logic OR operation on at least two criteria or on all threecriteria, so that in the case when one of the three criteria is met, theenvironment of the pass-through destination is defined by thiscriterion, and a point situated on the route segment currentlycalculated and inside this environment around the pass-throughdestination currently being considered becomes the end point of theroute segment.

[0074] A first criterion defining the circumscribed area around thepass-through destination is a circle around the intermediate destinationwhich is fixedly specified by a certain distance value of 20 km, forexample. Thus, if the route calculation gets within the intendeddistance value of 20 km, for example, to the pass-through destination,then the point reached is regarded as the end point of the routecalculation of the route segment currently being calculated. In the caseof the example described above, the route calculation would thus beterminated on reaching a straight line distance of 20 km from the citycenter of the first pass-through destination, Karlsruhe, on the A8freeway. The end point of the route segment calculated last, situated onthe A8 freeway, 20 km away from the city center of Karlsruhe, would bethe starting point for calculating the next route segment to the nextintermediate destination, namely Landau in the present case.

[0075] The path description of the first route segment calculated up tothe route segment calculated according to the criterion for determiningthe circumscribed area around the pass-through destination according tothe first exemplary embodiment would be as follows, the last entry beingbased not on measurement results but instead on rough estimates. TotalTime km km Δ Description Turn Road Direction 00:00 0 0.1 Start onBregenzer Strasse NW A81 00:00 0.1 1.1 — on — SW A81 00:03 0.2 1.5 — onB295/Föhrich W A81 strasse 00:06 2.7 1.5 — continue on B295 W A81 00:084.2 3.1 — on B295/Ditzinger W A81 Strasse 00:14 7.3 0.5 — continue onB295/Weilimd-orfer W A81 Strasse 00:15 7.8 6.7 AS Stuttgart- bear toleft A81/E41 S A81 Feuerbach to (18) 00:19 14.5 52 AD Leonberg continueA8/E52 SW A8 (49)(19) right, at 00:40 60.0 2 — continue on A8/E52 NW A8

[0076] A second criterion defining the circumscribed area around thepass-through destination is a distance value which is derived from thelength of the route segment calculated previously or, as an alternative,the sum of lengths of the route segments calculated previously andamounting to 5% of the length of the route segment(s) calculatedpreviously, for example. In the case of the example of a planned tripfrom Stuttgart-Feuerbach to Saarlouis by way of Karlsruhe, Landau andPirmasens, as described above, the circumscribed area around the citycenter of Karlsruhe would thus amount to 5% of the distance from thestarting point Stuttgart-Feuerbach to the current position. The endpoint of the route segment currently being calculated would thus besituated inside this circumscribed area and would then be set in step165 as the starting point for calculating the next route segment to thenext pass-through destination, namely Landau. A variant of the secondcriterion may involve the distance value which defines the circumscribedarea amounting to a specified amount of, for example, again 5% of thetotal length of the trip route. Since the total length of the trip routeat the time of the route calculation is not yet known, the straight linedistance between the starting location and the destination location orthe segment length of the trip route calculated without userspecification of pass-through destination locations may be used as asubstitute for this in rough approximation.

[0077] A third criterion for establishing the circumscribed area aroundthe pass-through destination is a change in class or in the case of aroad a change in the road class of a traffic route to be used, thischange being required to reach the pass-through destination, inparticular a change to a traffic route of a lower class. Such a changein road class would be, for example, leaving a freeway to enter afederal, state, county or other road or driving on a local through roadafter being on a federal road. In the example given above of the plannedtrip from Stuttgart-Feuerbach to Saarlouis by way of the pass-throughdestination of Karlsruhe, on reaching the freeway cloverleaf, it isnecessary to change to freeway A5, traveling in the direction ofFrankfurt, and after traveling a short distance on A5, it is necessaryto leave the freeway and enter a road of a lower road class incomparison with the A5 freeway driven on last. Thus in the present case,the circumscribed area around the pass-through destination would bedefined by this departure from the A5 freeway which represents the endpoint of the route calculation for the route segment currently beingcalculated. A subsequent route segment would thus be determined from theaforementioned departure from A5 to the next pass-through destination ofLandau.

[0078] The route description of the first route segment calculatedaccording to the criterion for determining the circumscribed area aroundthe pass-through destination according to the third exemplary embodimentwould be as follows, but the last entry would no longer belong to theroute segment and is shown here only for the purpose of illustration.Total Time km km Δ Description Turn Road Direction 00:00 0 0.1 start onBregenzer Strasse NW A81 00:00 0.1 1.1 — on — SW A81 00:03 1.2 1.5 — onB295/Föhrich W A81 strasse 00:06 2.7 1.5 — continue on B295 W A81 00:084.2 3.1 — on B295/Ditzinger W A81 Strasse 00:14 7.3 0.5 — continue onB295/Weilimdorfer W A81 Strasse 00:15 7.8 6.7 AS Stuttgart- bear to leftA81/E41 S AD Feuerbach on Leonberg (18) 00:19 14.5 52 AD Leonbergcontinue A8/E52 SW A8 (49)(19) right on 00:48 66.8 2 AD Karlsruhecontinue A5/E35 W A5 (46)(41) right on 00:50 68.8 0.2 AS Karlsruhe-continue — N A65 Mitte right on (45)

[0079] The list of possible embodiments of the criterion for definitionof the circumscribed area of the pass-through destination is notdefinitive. Other embodiments of the criterion are also conceivable andare within the scope of the present invention. In particular,combinations of the criteria are conceivable, e.g., such that thecriterion defining the widest circle also defines the circumscribedarea.

[0080] An especially advantageous embodiment of such a combinatorycriterion is a change in road class within a circle around thepass-through destination which is specified by a specified distancevalue and is necessary for reaching the pass-through destination. Inconcrete terms, such a criterion may be a change in road class within adistance of 15 km from the pass-through destination, this change beingnecessary to reach the pass-through destination. To do so, the partialroute calculated as a provisional route as described above would bechecked for a change in road class, in particular to a road class of alower order, i.e., for example, from freeway to federal or state roadswithin the specified straight line distance from the exact pass-throughdestination. In the present case, the exit AS Karlsruhe (45) from the A5freeway to the county road K9657 within the circle of 15 km from thecenter of the city would thus be determined as the first intermediatedestination point and thus the end point for the first partial route.After successful calculation of the first route segment, the startingpoint for calculation of another route segment would be equated with theend point of the route segment described above (step 165). Aftercalculating the first route segment according to the above example fromStuttgart-Feuerbach to the vicinity of Karlsruhe, the new starting pointwould be said end point in the vicinity of Karlsruhe; after calculationof the second route segment it would be an end point in the area of thesecond pass-through destination of Landau, and after calculation of thethird route segment it would be the end point of the third route segmentin the vicinity of Pirmasens.

[0081] If no other pass-through destination points taken into accountfor the preceding route segment calculation are present in destinationmemory 18, which is checked by the controller in step 170, then the lastroute segment, namely starting from the current starting point, i.e.,the end point of the route segment calculated last, to the destinationlocation is calculated (step 175).

[0082] The calculated route is formed after completion of the routecalculation of the route's last route segment by arranging thecalculated route segments in a sequence (step 180). Controller thencauses the complete trip route to be output on the display device ofuser interface 16 (step 125).

[0083] However, if it is found in step 170 that additional pass-throughdestination locations in addition to that already taken into account forthe route calculation are stored in destination memory 18, then thepass-through destination is equated with the next of the additionalpass-through destinations (step 185) and subsequently the route segmentfrom the new starting point, namely the end point of the route segmentcalculated last, to the pass-through destination is calculated (step160).

[0084] The sequence then goes to step 165 and the following steps, asdescribed above.

[0085] In the above-described example of a planned trip fromStuttgart-Feuerbach to Saarlouis via the pass-through destinations ofKarlsruhe, Landau and Pirmasens specified by the user in step 145 viauser interface 16, this yields a trip route as shown below in thefollowing route description on the basis of the procedure described herefor route calculation.

[0086] Path description of the trip route according to user definitionof the pass-through destinations Karlsruhe, Landau and Pirmasens: TotalTime km km Δ Description Turn Road Direction 00:00 0 0.1 start onBregenzer Strasse NW A81 00:00 0.1 1.1 — on — SW A81 00:03 1.2 1.5 — onB295/Föhrich W A81 strasse 00:06 2.7 1.5 — continue on B295 W A81 00:084.2 3.1 — on B295/Ditzinger W A81 Strasse 00:14 7.3 0.5 — onB295/Weilimdorfer W A81 Strasse 00:15 7.8 6.7 AS Stuttgart- bear to leftA81/E41 S AD Feuerbach to Leonberg (18) 00:19 14.5 52 AD Leonbergcontinue A8/E52 SW A8 (49)(19) right on 00:48 66.8 2 AD Karlsruhecontinue A8/E35 W A5 (46)(41) right on 00:50 68.8 0.2 AS Karlsruhe-Mittecontinue — N A65 (45) right on 00:50 69 1.1 — straight — NE A65 ahead on00:51 70.1 2.5 — continue on K9657 NW A65 00:52 72.6 0.8 — on EdeltrudTunnel W A65 00:54 73.4 11 — on K9657 W A65 01:00 83.9 24 AK Wörthercontinue on A65 W A65 intersection (3) 01:14 108.2 0.5 AS Landau northcontinue — N A8 (15) right on 01:15 108.7 13 — on — W A8 01:28 121.4 6.4— bear to B10 SW A8 right on 01:40 127.8 0.1 in roundabout continue B48NW A8 traffic, 16^(th) exit right on ramp 01:40 127.9 0 — bear to leftB48 SW A8 on 01:40 127.9 15 — bear to B10 NW A8 right, on 01:56 142.54.7 — half right B10 W A8 on 02:01 147.2 12 — straight B10 W A8 ahead on02:18 159.2 0.1 AS Pirmasens continue A8 NW AK (15) right on Neunkirchen02:18 159.3 30 — bear to A8 N AK right on Neunkirchen 02:35 189.4 7.9 AKNeunkirchen continue on A8 NW A8 (8)(27) 02:40 197.3 6.3 AD Neunkirchen/continue on A8 W A8 Spiesen (23) 02:44 203.6 5.9 AD Friedrichsthalcontinue on A8 NW A8 (20)(1) 02:47 209.5 19 AK Saarbrücken continue onA8 NW A8 (143)(17) — 02:57 228.5 0.1 AS Saarwellingen continue — N —(13) right, on 02:57 228.6 0.1 — continue on — N — 02:58 228.7 1.2 ASSaarwellingen bear to left B405 SW — (13) at end of road on 02:59 229.91.9 — on B405/Lebacher SW — Strasse 03:04 231.8 0.8 at end of road bearto B405/B511/ W — right on Banhofstrasse 03:06 232.6 0.4 — continue onB51/Schanzen W — strasse 03:06 233 0.4 — bear to left B51/ SW — onHoltzendorfer Strasse 03:08 233.4 0.6 — on Holtzendorfer SW — Strasse03:09 234 0.3 — on Deutsche Strasse SE — 03:10 234.3 0.1 — onFranzösische SE — Strasse 03:11 234.4 — destination — — — —

[0087] As shown by the path description for the trip route calculated onthe basis of the pass-through destinations specified by the user, itleads over other traffic routes than the trip route calculated withoutcorresponding user specifications. The calculated alternative trip routeaccording to trip instructions leads onto the A81 freeway, traveling inthe direction of Karlsruhe, via the A8 freeway, traveling in thedirection of Karlsruhe, through Karlsruhe in the direction of Landau onA65 and from there over the B10 in the direction of Pirmasens and fromthere over A6 and the extension thereof, A620, to Saarlouis.

[0088] Thus by specifying the pass-through destinations, a differentroute course is forced such that the route leads through a vicinity ofthe intermediate destinations which is specified according to thecriterion given above. In the present case, including federal road B10yields a much shorter route length in comparison with the trip routecalculated without user specifications, although at the expense of apossibly longer trip duration, as is apparent from a comparison of thepath descriptions.

[0089] The method described here makes available a trip route forsubsequent navigation so that the driver of the vehicle is directedalong this route by acoustic and/or visual driving instructions. If thedriver of the vehicle leaves the calculated trip route due to failure tofollow a trip instruction or an unforeseen driving maneuver and ifreturning to the trip route calculated originally is impossible or toocomplicated, e.g., when driving onto an autobahn in the wrong directionor something similar, it may be necessary to recalculate the route. Forsuch a recalculation of route, the current vehicle location at thatmoment is regarded as the starting point and the recalculation of theroute is otherwise performed in the manner already described. As analternative, it is also possible in this situation for the pass-throughdestinations specified by the user to be further taken into account forthe required recalculation, in which case the user is given anopportunity through display or output of the recalculated route (in step125) to delete originally specified pass-through destinations whichmight be considered inappropriate for the recalculated route becausethey are associated with detours, for example, by entering newpass-through destinations (in step 145).

[0090] The method according to the present invention may be used as partof an advance calculation of the trip route at the starting location andalso in the form of an online route calculation during navigation. Theonline route calculation may be carried out in such a manner that theroute is first calculated from the starting location to the firstpass-through destination. The driver of the vehicle is then guided intothe circumscribed area of the pass-through destination, depending on theroute segment calculated. On reaching the circumscribed area of thepass-through destination defined according to the criterion given above,the calculation of the next route segment from the current vehiclelocation which is in the circumscribed area of the pass-throughdestination to the next pass-through destination or to the destinationcity is begun in the manner indicated.

[0091] In addition, the method according to the present invention mayalso be applied to offboard route calculations in such a way that theroute segments are calculated by a service provider after transmissionof the starting location determined or the current location, thedestination specified by the user and the user-defined pass-throughdestinations via air interface 15, on the basis of traffic routeinformation available to the service provider and, if necessary,additional information about the condition of the traffic routes. Theroute segments or the information describing them, such as interpolationpoints to be reached, on the basis of which the onboard navigationdevice fixedly installed in the vehicle interpolates a trip route, isthen transmitted by the service provider via air interface 15 to onboardnavigation device 1 for the purpose of navigation and is stored there.

What is claimed is:
 1. A method for calculating a route from a startinglocation to a destination location, wherein after specifying at leastone pass-through destination location, a pass-through destination pointis determined automatically for each of the at least one pass-throughdestination location, this pass-through destination point being situatedin a circumscribed area of the at least one pass-through destinationlocation, determined by a specified criterion, and the route iscalculated via the at least one pass-through destination point.
 2. Themethod as recited in claim 1, wherein in a first step, the startinglocation is set as the starting point for the route calculation, and afirst pass-through destination location of the at least one pass-throughdestination location is set as the pass-through destination; in a secondstep, a route segment is calculated from the starting point to thepass-through destination point which is determined automatically and issituated in an interception range about the pass-through destination,determined according to the criterion specified; in a third step, theend point (=pass-through destination point) of the previously calculatedroute segment is set as the starting point for the calculation of anadditional route segment; in the case of additional pass-throughdestination locations, the next pass-through destination location of theat least one pass-through destination location is set as thepass-through destination, and the process is continued with the secondstep; in the case of no additional pass-through destination locations,in a fourth step the route segment is calculated from the startingpoint, set in the third step, to the destination location; and the routeis obtained by arranging the calculated route segments in a sequence. 3.The method as recited in claim 1 or 2, wherein the specified criterionis a predefined distance from the pass-through destination.
 4. Themethod as recited in claim 3, wherein the specified distance is afixedly specified or specifiable distance value.
 5. The method asrecited in claim 3, wherein the specified distance is derived fromcalculated route information, in particular the calculated route length.6. The method as recited in claim 3, wherein the specified distance is afixedly specified or specifiable distance value or it is derived fromcalculated route information, in particular the calculated route length,depending on which criterion defines a wider circumscribed area.
 7. Themethod as recited in claim 1 or 2, wherein the specified criterion is achange in road class which is necessary to reach the pass-throughdestination.
 8. The method as recited in claim 7, wherein the specifiedcriterion is a change in a road class to a road of a lower class road,this change being necessary to reach the pass-through destination. 9.The method as recited in claim 1 or 2, wherein the specified criterionis a change in road class which is necessary for reaching thepass-through destination as recited in claim 6 or 7, within a specifieddistance from the pass-through destination as recited in one of claims 3through 6.